656 Part IV Drawing in Three Dimensions

Tip	As soon as you have a separate layer for the hidden portion of the model, you can modify
	that layer’s color and/or linetype to show the hidden lines in a contrasting color or linetype.

Summary

In this chapter, I covered all the ways to view your 3D drawing. You read about:

Using the standard viewpoints on the Viewpoint flyout for a quick look

Utilizing the DDVPOINT command to specify exact angles

Using the tripod and compass for flexibility

Using the PLAN command to quickly return you to plan view

Shading your drawing in one of several modes — these shading modes persist until you turn them off.

Applying 3D orbit to view your model from any position. You can zoom and pan, create parallel and perspective views, and set clipping planes. You can also create a continuously moving orbit.

Using the DVIEW command to let you create parallel and perspective views. You set the camera and target where you can create front and back clipping planes.

Employing the three commands — SOLVIEW, SOLDRAW, and SOLPROF — that help you lay out views of a 3D drawing for plotting

In the next chapter, I explain how to create 3D surfaces.

Creating 3D

Surfaces

In this chapter, you learn to create all types of surfaces, also called meshes. Surfaces have a great advantage over 3D wireframe models

because you can hide back surfaces and create shaded images for easier visualization of your models. Surfaces also enable you to create unusual shapes, such as for topological maps or free-form objects.

This entire chapter applies to AutoCAD only. For information on surfaces that AutoCAD LT can create, see Chapter 21.

Figure 23-1 shows a lamp created by using surfaces.

Figure 23-1: A lamp created with surfaces.

23C H A P T E R

In This Chapter

Drawing surfaces with 3DFACE and PFACE

Creating 3D polygon meshes

Drawing standard 3D shapes

Drawing a revolved surface

Creating extruded, ruled, and edge surfaces

658 Part IV Drawing in Three Dimensions

You cannot obtain information about physical properties — such as mass, center of gravity, and so on — from surfaces. Such information can be obtained only from 3D solids, which are covered in the next chapter.

AutoCAD approximates curved surfaces by creating a mesh of planes at varying angles. You see the planes because AutoCAD displays them using a web of intersecting lines. AutoCAD defines the mesh by its vertices — where the lines intersect. Figure 23-2 shows a mesh with its vertices.

Figure 23-2: A surface mesh.

When working with surfaces you may want to display the Surfaces toolbar. Right-click any toolbar and choose Surfaces.

Drawing Surfaces with 3DFACE

Two-dimensional objects are often used to create three-dimensional models. In Chapter 21, I discuss how you can use 2D solids (the SOLID command), wide polylines, and circles to make horizontal surfaces when you add a thickness to them. In fact, the SOLID command is so useful in 3D that you can find its icon on the Surfaces toolbar.

You can also use regions in 3D drawings. Although regions are 2D objects and cannot be given a thickness, when you use the HIDE command, AutoCAD displays the region as a surface. When the drawing is regenerated to a wireframe display, the region is displayed as a wireframe again, losing its surface properties.

Another option is to use 3DFACE, which is a true 3D command. 3DFACE creates threeor foursided surfaces that can be in any plane. You can place surfaces together to make a many-sided surface. While AutoCAD draws lines between these surfaces, you can make the lines invisible to create the effect of a seamless surface. You define the surface by specifying the points that create the corners of the surface. As a result, a 3D face cannot have any curves. 3DFACE only creates surfaces — you cannot give a thickness to a 3D face. However, you can create a 3D solid from a 3D face using the EXTRUDE command. 3D solids are covered in the next chapter.

Chapter 23 Creating 3D Surfaces 659

Using the 3DFACE command

To create a 3D face, choose 3D Face from the Surfaces toolbar. AutoCAD prompts you for first, second, third, and fourth points. You must specify points clockwise or counterclock-

wise, not in the zigzag fashion required by the 2D SOLID command. When creating a 3D face:

Press Enter at the Specify fourth point or [Invisible] <create three-sided face>: prompt to create a three-sided surface. Then press Enter again to end the command.

To create a four-sided surface, specify a fourth point. AutoCAD repeats the Specify

third point or [Invisible] <exit>: prompt. Press Enter to end the command.

To create surfaces of more than four sides, continue to specify points. AutoCAD repeats the thirdand fourth-point prompts until you press Enter — twice after a third point or once after a fourth point.

As you continue to add faces, the last edge created by the third and fourth points becomes the first edge of the new face so that adding a face requires only two additional points.

Tip	It often helps to prepare for a complex 3D face by creating 2D objects for some or all of the
	faces. You can then use Endpoint object snaps to pick the points of the 3D face. Place these
	2D objects on a unique layer, such as Frames or Const.

Making 3D face edges invisible

Making edges invisible makes a series of 3D faces look like one 3D face. Figure 23-3 shows three 3D faces with and without internal seams.

	Figure 23-3: You can make internal edges
All edges visible	of a 3D face invisible.

Internal edges invisible

You can control the visibility of 3D face edges in several ways.

Controlling visibility during 3D face creation

While you’re drawing the 3D face, you can right-click and choose Invisible before each edge. Then specify the next point. However, it’s sometimes difficult to predict exactly where to indicate the invisible edge.

660 Part IV Drawing in Three Dimensions

Using the EDGE command

After creating the entire 3D face, you can use the EDGE command. The sole purpose of the EDGE command is to make 3D face edges visible and invisible — this is probably the easiest way to control the visibility of 3D face edges.

Choose Edge from the Surfaces toolbar. At the Specify edge of 3dface to toggle visibility or [Display]: prompt, select a visible edge that you want to make invisi-

ble. AutoCAD repeats the prompt so that you can select additional edges. Press Enter to make the edges invisible. Although a visible edge might actually be two edges belonging to two adjacent 3D faces, EDGE makes them both invisible.

To make invisible edges visible, right-click and choose the Display option. AutoCAD displays all the edges in dashed lines and shows the Enter selection method for display of hidden edges [Select/All] <All>: prompt. Press Enter to display all the edges or use the Select option to select 3D faces (you can use windows for selection). Either way, you see the edges of the 3D face you want to edit. AutoCAD then repeats the Specify edge of

3dface to toggle visibility or [Display]: prompt. You can now select the edge you want to make visible. Press Enter to end the command and make the edge visible.

Using the Properties palette

After creating one or more 3D faces, you can also open the Properties palette (choose Properties on the Standard toolbar) and select one 3D face. You can choose more than one, but the results are difficult to predict.

Using this palette to edit 3D face edge visibility presents two difficulties. First, you have no easy way of knowing which edge is which, because the palette only labels them Edge 1, 2, 3, and 4. Second, although the EDGE command makes both edges of adjacent 3D faces visible or invisible, the Properties palette does not. You need to use it for each adjacent face. The best method is to use the EDGE command to control visibility of 3D face edges.

Using the SPLFRAME system variable

Setting the SPLFRAME system variable to 1 and then regenerating the drawing makes all 3D face edges visible. (The SPLFRAME system variable also affects the display of spline-fit polylines, hence its name.) To return edges to their original setting, set SPLFRAME to 0 and do a REGEN.

On the	The drawing used in the following Step-by-Step exercise on drawing 3D faces, ab23-a.dwg,
CD-ROM	is in the Drawings folder on the CD-ROM.

STEP-BY-STEP: Drawing 3D Faces

1.Open ab23-a.dwg from the CD-ROM.

2.Save it as ab23-01.dwg in your AutoCAD Bible folder. This is a blank drawing with architectural units. Turn on ORTHO. OSNAP should be on. Set running object snaps for endpoints and midpoints. If the Surfaces toolbar is not displayed, right-click any toolbar, and check Surfaces.

Chapter 23 Creating 3D Surfaces 661

3. Choose 3D Face from the Surfaces toolbar. Follow the prompts:

Specify first point or [Invisible]: 6,6 Specify second point or [Invisible]: @20,0

Specify third point or [Invisible] <exit>: @0,2'

Specify fourth point or [Invisible] <create three-sided face>:

@–20,0

Specify third point or [Invisible] <exit>:

4.Start the COPY command. Follow the prompts:

Select objects: Select the 3D face. Select objects:

Specify base point or displacement, or [Multiple]: Right-click and choose Multiple.

Specify base point: Pick any point.

Specify second point of displacement or <use first point as displacement>: @0,0,1.5'

Specify second point of displacement or <use first point as displacement>: @0,0,3'

Specify second point of displacement or <use first point as displacement>:

You don’t see any difference because you’re looking at the three 3D faces in plan view and they’re on top of each other.

5.Choose View 3D Views SE Isometric. Your drawing should look like Figure 23-4. You now have the top, bottom, and middle shelf of the cabinet.

3

6

2

7

4

5

1

8

Figure 23-4: The three 3D faces from an isometric viewpoint.

6. Start the 3DFACE command again. Follow the prompts:

662 Part IV Drawing in Three Dimensions

Specify first point or [Invisible]: Pick the endpoint at 1 in Figure 23-4.

Specify second point or [Invisible]: Pick the endpoint at 2. Specify third point or [Invisible] <exit>: Pick the endpoint at 3. Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 4.

Specify third point or [Invisible] <exit>: Pick the endpoint at 5. Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 6.

Specify third point or [Invisible] <exit>: Pick the endpoint at 7. Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 8.

Specify third point or [Invisible] <exit>:

7.To draw the door of the cabinet, change the current layer to CONST. Start the LINE command and draw a line from 2 in Figure 23-4 to @18<225. End the LINE command. Now start the COPY command and copy the line from 2 to 1. These two construction lines frame the door.

8.To make it easier to work on the door, choose Tools New UCS 3 Point. Follow the prompts:

Specify new origin point <0,0,0>: Pick the left endpoint of the bottom construction line.

Specify point on positive portion of X-axis <-0'-5 3/4",-0'-6 3/4", 0'-0">: Pick 1 in Figure 23-4.

Specify point on positive-Y portion of the UCS XY plane <-0'-7 7/16", -0'-6",0'-">: Pick the left endpoint of the top construction line.

9.Start the LINE command again. Follow the prompts:

Specify first point: Choose the From object snap.

Base point: Pick the left endpoint of the top construction line.

<Offset>: @3,–3

Specify next point or [Undo]: Move the cursor to the right and type

12 .

Specify next point or [Undo]: Move the cursor down and type 30 .

Specify next point or [Close/Undo]: Move the cursor to the left and type 12 .

Specify next point or [Close/Undo]: c

Your drawing should look like Figure 23-5.

10.Change the current layer to 0. Choose 3D Face from the Surfaces toolbar. Follow the prompts:

Specify first point or [Invisible]: Pick the endpoint at 1 in Figure 23-5.

Specify second point or [Invisible]: Pick the endpoint at 2 in Figure 23-5.

Specify third point or [Invisible] <exit>: Pick the endpoint at 3. Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 4 in Figure 23-5. Notice the edge lines between 1 and 2 and between 3 and 4.

Chapter 23 Creating 3D Surfaces 663

Specify third point or [Invisible] <exit>: Right-click and choose Invisible. Pick the endpoint at 5 in Figure 23-5.

Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 6.

Specify third point or [Invisible] <exit>: Right-click and choose Invisible. Pick the endpoint at 7.

Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 8.

Specify third point or [Invisible] <exit>: Pick the endpoint at 1 in Figure 23-5.

Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 2.

Specify third point or [Invisible] <exit>:

5 8

6 7

3

2

4 1

Figure 23-5: The partially completed cabinet.

11.Choose Edge from the Surfaces toolbar. At the Specify edge of 3dface to toggle visibility or [Display]: prompt, pick the edge between 1 and 2

and then the edge between 3 and 4. (A midpoint marker and SnapTip appear.) Press Enter. The edges disappear.

12.Choose Tools New UCS World.

13.Choose View 3D Views Viewpoint Presets to open the Viewpoint Presets dialog box. Set the From: X Axis angle to 200 degrees. Set the XY Plane angle to 35 degrees. Choose OK.

14.Choose View Hide to see the result. You can clearly see through the window of the cabinet door.

15.Save your drawing. It should look like Figure 23-6.